I used to have so much trouble remembering this rule.
Chicago says that when two nouns “possess” the same entity, only the second takes an apostrophe (‘):
my aunt and uncle’s house
Gilbert and Sullivan’s lolanthe
Minneapolis and Saint Paul’s transportation system
On the other hand, when two nouns possess different entities, both possessives take an apostrophe:
my aunt’s and uncle’s specific talents
New York’s and Chicago’s transportation systems
our friends’ and neighbors’ children
Isn’t that neat?
If any writing questions have you stumped, send them in. I’ll check them out for you.
Tara’s Writing Studio